The new interference slide proposed for immuno-assays produces the desired color changes in a wet state. Developing this technique brings assays closer to a one step process than current technology, including our own dry interference slide. Without the rinsing and drying steps, the wet technique will be simpler and faster than ELISA. The entire assay can be contained inside an impermeable envelope, therefore reducing the risk of contamination. This technique will also lend itself to producing a panel test with a single applied sample. The inherent accuracy and reproducibility of optical methods and techniques eliminates the dilution series and controls. This advantage will reflect in the handling time and end costs of the test. The preliminary calculations indicate the wet slide will be 3-4 times more sensitive than the dry slide. Sensitivity will be in the range of 10Ng/cm2. After the completion of Phase I, it will be evident that the proposed slide functions properly. A practical assay system can be specified and a cost estimate can be produced for Phase II. This new technique and a market research will form a base for commercial development and production.